Hahaha good question

I just made a quick example in gimp. It's like this without any graytones, just black and white. In photoshop it's called 'stamp' so i hoped you just knew it. It's basically the dark areas that get pitch black and the light areas that get all white. i like the effect for portraits



Hope this makes sense otherwise i have to make a example on a pc with photoshop wich i don't have on this one i'm using at the moment